ReactNative is a Native Framework... I will also say that we are using React Native, so I know that done properly this will work.
So normally, your developers would provide you with the deeplink that they configured.... so for our apps, let's say I have three apps called App A, App B, and App C
In our case, each app was configured with a deep link named for the app, so I would use:
As my deeplinks... (of course those deeplinks could go farther, like to specific pages in the app), but for Assurance testing, you really just need the root.
I am not sure how you got the deeplink you are testing... but if the deeplink tester isn't working, it's probably not going to work for Assurance either...
Can you confirm that Deeplinking has been enabled on your app? And can you get the developers to confirm that the deeplink you are trying to use is correct?